As gear machining equipment, there are gear shaping machines and hobbing machines configured to manufacture a gear by cutting, gear grinding machines configured to grind a quenched gear, and the like.
In machining a gear with such gear machining equipment, at least one gear taken out from a lot having undergone the machining is subjected to gear measurement such as tooth profile and tooth trace measurement with a gear measuring device to check the machining accuracy. If the machining accuracy is good, the machining with the gear machining equipment is continued for the remaining lots. If the machining accuracy is poor, the machining accuracy of the gear machining equipment is corrected, and the remaining lots are then machined. Meanwhile, in a case of a large gear, producing a defective product is unacceptable. Thus, a stock amount is left on the gear, and gear machining with gear machining equipment and gear measurement with a gear measuring device are repeated several times, and after the final accuracy is checked, finishing is performed.
Conventional gear measuring devices are usually separate from gear machining equipment. In this case, a work of transferring a machined gear from the gear machining equipment to the gear measuring device is necessary. In this respect, in recent years, various types of gear machining equipment equipped integrally with a gear measuring device have been proposed for the purpose of eliminating the gear transferring work to improve the workability.
Meanwhile, as a measuring probe used in the gear measuring device, there are a continuous scanning probe and a touch probe. The continuous scanning probe is an analog measuring probe and configured to move its sensing element in continuous contact with the tooth surface of a gear and measure the tooth surface on the basis of the amount of displacement of the sensing element in the movement. On the other hand, the touch probe is a digital (ON/OFF type) measuring probe. The touch probe is superior to the continuous scanning probe in environmental resistances such as humidity resistance and dust resistance, and is therefore particularly useful in a case where the gear measuring device is provided on the gear machining equipment. Moreover, the touch probe is lower in cost than the continuous scanning probe, and is therefore very useful from the viewpoint of cost reduction of the gear machining equipment.
To describe the touch probe on the basis of FIG. 11, a touch probe 1 is configured such that its sensing element 2 is normally held in a state shown by the solid line in FIG. 11. The touch probe 1 is turned on (in a case of an internal switch with a form a contact; the touch probe 1 is turned off in a case of a form b contact) as the sensing element 2 of the touch probe 1 approaches a tooth surface 3a of a gear 3 as shown by an arrow A, contacts the tooth surface 3a as shown by the dashed lines in FIG. 11, and is displaced by a pre-travel amount Δ (e.g., about several tens of μm). Then, the tooth profile and the tooth trace are measured on the basis of coordinates on drive axes at the moment when the touch probe 1 is turned on (or off), and the like.
Accordingly, to measure the next measuring point, it is necessary to move the sensing element 2 in a direction away from the tooth surface 3a as shown by an arrow B or move the tooth surface 3a in a direction away from the sensing element 2 to once turn off the touch probe 1 (in the case of the internal switch with the form a contact; the touch probe 1 is turned on in the case of the form b contact).
To describe these actions on the basis of FIG. 12, in a case of measurement at measuring points P1 to P4 on the tooth surface 3a for example, the touch probe 1 is first moved in an X-axis direction to set the sensing element 2 to a position corresponding to the first measuring point P1. Then, the sensing element 2 is moved in a Y-axis direction or the gear 3 is turned about a C axis (the rotation center of the gear 3) to bring the sensing element 2 closer to the tooth surface 3a as shown by an arrow A and further into contact with the measuring point P1, so that the touch probe 1 is turned on (the case with a form a contact is described here). Subsequently, the sensing element 2 is moved backward along the Y axis or the gear 3 is turned backward about the C axis to separate the sensing element 2 from the tooth surface 3a as shown by an arrow B, so that the touch probe 1 is turned off and returned to the initial set position. Thereafter, the sensing element 2 is moved in the X-axis direction as shown by an arrow D and set to a position corresponding to the second measuring point P2. In the subsequent process, the same actions are repeated for each of the measuring points P2 to P4.